Optical disks are a common medium for use with data storage devices. Optical disks typically have data patterns embedded on one side of the disk, designated the bottom side, and eye-visible patterns printed on the other side of the disk, designated the top side. The printed patterns on the top side of a disk are typically in the form of text and/or graphics that present information related to the embedded data that is stored on the bottom side of the disk or relating to the source of the disk. Traditionally, optical disks have contained read only memory (ROM) in which the embedded data patterns on the bottom side of the disk do not change. Since the embedded data on the bottom side of the disk does not change, the text and/or graphics present on the top side of the disk may be printed one time only, with all of the text and/or graphics included in the single printing session. However, there are applications in which it is desirable to have two or more non-overlapping print sessions that generate eye-visible material on such disks.
Moreover, writeable optical disks and disk drive systems have been developed that allow a disk to be written with new embedded data after the initial production of the disk. With new data being embedded on the bottom side of the disk, there is a need to print new related text and/or graphics on the top side of the disk. In many cases the disk already has some text and/or graphics printed on the top side, and as a result, new text will only be appropriately located on certain areas of the disk. In addition, the pre-printed visible material often has a particular orientation, including rotation and translation components, that dictates the acceptable orientation of new visible material that is to be printed. When loading a large group of pre-printed disks into a printing device, it is difficult and time-consuming to manually align the pre-printed patterns of each disk so that the printer will print the new material in the same designated area of each successive disk.
A known solution to the problem of aligning pre-printed disks to avoid printing misaligned material involves placing a visible reference mark on each disk. The reference marks are used to align disks relative to a printer during each printing of visible material onto the disks. Specifically, an optical sensor is used to locate the reference mark on a disk. The disk is mechanically rotated until the reference mark is positioned such that the orientation of the pre-printed pattern on the disk is properly aligned with a printing device. The properly aligned disk is then imprinted with the new material such that the new material is located in the designated area of the disk and properly oriented with the pre-printed material on the disk.
Disadvantages of the above-described technique are that extra effort is required to print the reference mark on-the disk and that the reference mark creates a permanent blemish on the disk. An additional disadvantage is that mechanically rotating a disk requires additional equipment that would not be necessary if the rotational position of the disk were not changed.
There is also known prior art related to the problem of aligning randomly oriented CD-ROM disks that are to be loaded into protective sleeves or jewel cases. The known solution involves imaging a perfectly oriented disk and generating reference image data from the perfectly aligned disk. The reference image data is then compared to image data generated for a disk just before the disk is loaded into its protective sleeve. Based on the comparison, the target disk is mechanically rotated until the disk is properly oriented and then the disk is placed into its respective sleeve.
Once new material has been printed onto a disk, it is desirable to check the quality of the printed image. A system for checking the quality of a printed image on an optical disk is disclosed in U.S. Pat. No. 5,181,081, entitled "Print Scanner," issued to Suhan. Although Suhan discloses a system for checking the quality of a printed image, Suhan is only able to check the quality of the complete image on a disk by comparing the image to another complete image taken from a different disk. As a result, if the initial image has a printing defect, the defect becomes part of the reference image. In addition, Suhan is only able to check the quality of images that have the exact same orientation with respect to the printing and imaging apparatus.
As a result of the stated shortcomings, what is needed is a system and method for printing new textual and/or graphical material into a designated area of a randomly oriented and pre-printed substrate that does not require the substrate to have extraneous markings and that does not require the substrate to be mechanically rotated for printing. In addition, what is needed is a system and method for checking the quality of a newly printed disk that contains new visible material and pre-printed visible material.